Successful and predictable rehabilitation of missing teeth with dental implants has been reported in hosts with normal bone volume and density. Two remaining areas where improved techniques and materials are sought include: (1) implant failures in low density/volume bone typically found in elderly and/or medically compromised patients, and (2) peri-implantitis as a complication of dental implant procedures.
A study on Branemark implants found that only 3% of implants placed in type 1, 2 and 3 bone were lost after 5 years, while in type 4 bone, which is low density bone, failure rates were 35% over the same period. Lack of dense cortical bone and the sparse existing hard trabecular bone can fracture during surgical drilling. Self-threading dental implants can also be unstable in this type of bone. The poor healing and bone producing capacity of elderly and/or medically compromised patients further reduces implant success rates.
FIG. 1 shows undecalcified slides of an 85-year old male fresh cadaver. The slide in (a) shows a dental implant in anterior maxilla with intimate contact to the cortical bone. The slide in (b) shows a dental implant in posterior maxilla (type 4 bone) and shows thin cortical bone and sparse trabecular bone around the implant. Implants placed in weak bone like this (b) often do not achieve initial stability and tend to fail more frequently.
When initially unstable implants are encountered, dental surgeons can replace unstable implants with wider implants provided there is enough resident bone available for this. In many cases this technique fails because available bone is hard but weak. Consequently, wider implants can lead to fracture of surrounding trabeculae, thereby causing another unstable implant situation. In loose implants, interfacial micromotion greater than 100 to 150 μm induces soft tissue formation instead of bone formation around implants, which is regarded as a failure.
In addition to mechanical issues with dental implants, peri-implantitis can be a significant problem for dental implant recipients, as can it's analog, periodontitits, for natural teeth. Peri-implantitis and periodontitis are characterized by inflammation of the mucosa and loss of supporting bone. These conditions can lead to complete loss of osseointegration and implant or tooth loss.
A few selected examples of shortcomings of existing procedures and bone cements have been listed. There exists a need for improved bone cements that address these, and other issues of existing bone cements. In particular, in the dental field, there exists a need for dental implant cement compositions which can physically fortify existing bone and repair previously applied failing dental implants in recipients.